Having used quite a few different ERP systems, I can safely say that once you know one or two, picking up others is easy. Though the menus may change, the core principles remain the same. There is yet a system I cannot work with.
My experiences have been in running reports, transitioning from one to another, diagnosing configuration issues, and creating training materials. In many cases, I have used MS Access and Excel to bridge gaps in reporting and data consolidation.